Marcus Radicke

On a dark-field signal generated by micrometer-sized calcifications in phase-contrast mammography

We show that a distribution of micrometer-sized calcifications in the human breast which are not visible in clinical x-ray mammography at diagnostic dose levels can produce a significant dark-field signal in a grating-based x-ray phase-contrast imaging setup with a tungsten anode x-ray tube operated at 40 kVp. A breast specimen with invasive ductal carcinoma was investigated immediately after surgery by Talbot-Lau x-ray interferometry with a design energy of 25 keV. The sample contained two tumors which were visible in ultrasound and contrast-agent enhanced MRI but invisible in clinical x-ray mammography, in specimen radiography and in the attenuation images obtained with the Talbot-Lau interferometer. One of the tumors produced significant dark-field contrast with an exposure of 0.85 mGy air-kerma. Staining of histological slices revealed sparsely distributed grains of calcium phosphate with sizes varying between 1 and 40 μm in the region of this tumor. By combining the histological investigations with an x-ray wave-field simulation we demonstrate that a corresponding distribution of grains of calcium phosphate in the form of hydroxylapatite has the ability to produce a dark-field signal which would-to a substantial degree-explain the measured dark-field image. Thus we have found the appearance of new information (compared to attenuation and differential phase images) in the dark-field image. The second tumor in the same sample did not contain a significant fraction of these very fine calcification grains and was invisible in the dark-field image. We conclude that some tumors which are invisible in x-ray absorption mammography might be detected in the x-ray dark-field image at tolerable dose levels.

Grating-based darkfield imaging of human breast tissue

Mastectomy specimens were investigated using a Talbot-Lau X-ray imaging set-up. Significant structures in the darkfield were observed, which revealed considerably higher contrast than those observed in digital mammography. Comparison with the histomorphometric image proofs that the darkfield signal correlates with a tumor region containing small calcification grains of 3 to 30μm size.

A Standard Mammography Unit – Standard 3D Ultrasound Probe Fusion Prototype: First Results

AIM The combination of different imaging modalities through the use of fusion devices promises significant diagnostic improvement for breast pathology. The aim of this study was to evaluate image quality and clinical feasibility of a prototype fusion device (fusion prototype) constructed from a standard tomosynthesis mammography unit and a standard 3D ultrasound probe using a new method of breast compression. MATERIALS AND METHODS Imaging was performed on 5 mastectomy specimens from patients with confirmed DCIS or invasive carcinoma (BI-RADS ™ 6). For the preclinical fusion prototype an ABVS system ultrasound probe from an Acuson S2000 was integrated into a MAMMOMAT Inspiration (both Siemens Healthcare Ltd) and, with the aid of a newly developed compression plate, digital mammogram and automated 3D ultrasound images were obtained. RESULTS The quality of digital mammogram images produced by the fusion prototype was comparable to those produced using conventional compression. The newly developed compression plate did not influence the applied x-ray dose. The method was not more labour intensive or time-consuming than conventional mammography. From the technical perspective, fusion of the two modalities was achievable. CONCLUSION In this study, using only a few mastectomy specimens, the fusion of an automated 3D ultrasound machine with a standard mammography unit delivered images of comparable quality to conventional mammography. The device allows simultaneous ultrasound - the second important imaging modality in complementary breast diagnostics - without increasing examination time or requiring additional staff.

Analytical and simulative investigations of moiré artefacts in Talbot-Lau X-ray imaging

Besides the well-known conventional X-ray attenuation image, Talbot-Lau X-ray imaging (TLXI) provides additional information about the small-angle scattering and refractive features of an object. In general, TLXI setups have to be mechanically robust, since already slight inaccuracies during the measurement process result in moire artefacts. This work derives moire artefacts as a result of phase-stepping inaccuracies. The dependency of these artefacts on the phase-stepping inaccuracies is mathematically derived by a Taylor series expansion and verified by a simulation. Among other things, it is shown that moire artefacts can be calculated by a weighted mean of phase-stepping position deviations to their target positions. These weighting factors vary for each image. Moire artefacts can even be affected by object features which are not displayed in the particular contrast. The findings of this work offer the possibility to develop advanced reconstruction algorithms which suppress moire artefacts in the reconstructed images. This reduces the method’s susceptibility to setup component inaccuracies as well as external influences and hence facilitates TLXI for clinical practice.

Single-shot Talbot–Lau x-ray dark-field imaging of a porcine lung applying the moiré imaging approach

Talbot-Lau x-ray imaging provides additionally to the conventional attenuation image, two further images: the differential phase-contrast image which is especially sensitive to differences in refractive properties and the dark-field image which is showing the x-ray scattering properties of the object. Thus, in the dark-field image sub-pixeled object information can be observed. As it has been shown in recent studies, this is of special interest for lung imaging. Changes in the alveoli structure, which are in the size of one detector pixel, can be seen in the dark-field images. A fast acquisition process is crucial to avoid motion artifacts due to heartbeat and breathing of the patient. Using moiré imaging the images can be acquired with a single-shot exposure. Nevertheless, the spatial resolution is reduced compared to the phase-stepping acquisition. We evaluate the results of both imaging techniques towards their feasibility in clinical routine. Furthermore, we analyse the influence of artificial linear object movement on the image quality, in order to simulate the heartbeat of a patient.

Enhanced reconstruction algorithm for moiré artifact suppression in Talbot–Lau x-ray imaging

Talbot-Lau x-ray imaging (TLXI) is an innovative and promising imaging technique providing information about the x-ray attenuation, scattering, and refraction features of objects. However, the method is susceptible to vibrations and system component imprecisions, which are inevitable in clinical and industrial practice. Those influences provoke grating displacements and hence errors in the acquired raw data, which cause moiré artifacts in the reconstructed images. We developed an enhanced reconstruction algorithm capable of compensating these errors by adjusting the grating positions and thus suppressing the occurrence of moiré artifacts. The algorithm has been developed with regard to a future application in medical practice. The capability of the algorithm is demonstrated on a medical data set of a human hand (post-mortem) acquired under clinical conditions using a pre-clinical TXLI prototype. It is shown that the algorithm reliably suppresses moiré artifacts, preserves image contrast, does not blur anatomical structures or prevent quantitative imaging, and is executable on low-dose data sets. In addition, the algorithm runs autonomously without the need of interaction or rework of the final results. In conclusion, the proposed reconstruction algorithm facilitates the use of TLXI in clinical practice and allows the exploitation of the methods full diagnostic potential in future medical applications.

Hairline fracture detection using Talbot-Lau x-ray imaging

Talbot-Lau X-ray imaging (TLXI) provides information about scattering and refractive features of objects – in addition to the well-known conventional X-ray attenuation image. We investigated the potential of TLXI for the detection of hairline fractures in bones, which are often initially occult in conventional 2D X-ray images. For this purpose, hairline fractures were extrinsically provoked in a porcine trotter (post-mortem) and scanned with a TLXI system. In the examined case, hairline fractures caused dark-field and differential-phase signals, whereas they were not evident in the conventional X-ray image. These findings motivate a comprehensive and systematic investigation of the applicability of TLXI for diagnosing hairline fractures.

Initial results of the FUSION-X-US prototype combining 3D automated breast ultrasound and digital breast tomosynthesis

PurposeTo determine the feasibility of a prototype device combining 3D-automated breast ultrasound (ABVS) and digital breast tomosynthesis in a single device to detect and characterize breast lesions.MethodsIn this prospective feasibility study, the FUSION-X-US prototype was used to perform digital breast tomosynthesis and ABVS in 23 patients with an indication for tomosynthesis based on current guidelines after clinical examination and standard imaging. The ABVS and tomosynthesis images of the prototype were interpreted separately by two blinded experts. The study compares the detection and BI-RADS® scores of breast lesions using only the tomosynthesis and ABVS data from the FUSION-X-US prototype to the results of the complete diagnostic workup.ResultsImage acquisition and processing by the prototype was fast and accurate, with some limitations in ultrasound coverage and image quality. In the diagnostic workup, 29 solid lesions (23 benign, including three cases with microcalcifications, and six malignant lesions) were identified. Using the prototype, all malignant lesions were detected and classified as malignant or suspicious by both investigators.ConclusionSolid breast lesions can be localized accurately and fast by the Fusion-X-US system. Technical improvements of the ultrasound image quality and ultrasound coverage are needed to further study this new device.Key PointsThe prototype combines tomosynthesis and automated 3D-ultrasound (ABVS) in one device.It allows accurate detection of malignant lesions, directly correlating tomosynthesis and ABVS data.The diagnostic evaluation of the prototype-acquired data was interpreter-independent.The prototype provides a time-efficient and technically reliable diagnostic procedure.The combination of tomosynthesis and ABVS is a promising diagnostic approach.

Towards cartilage diagnosis in X-ray phase-contrast interferometry

Osteoarthritis is a common cartilage disease, particularly in societies with aging population. Over 80% of the people over 75 years are affected in the USA. MRI and X-ray can be used to image cartilage, but both approaches suffer from specific drawbacks. X-ray Talbot-Lau interferometers (TLI) have the potential to unite benefits from both modalities. However, TLI setups require to be carefully designed for an imaging task, and the design process itself is not yet well understood. In this paper, we present an optimization framework for directly visualizing cartilage in the knee with phase-contrast imaging. First, we create simulated phantoms and make a setup-independent choice for an X-ray spectrum that maximizes the theoretically possible contrast to noise ratio over dose. Then, we analytically adapt a Talbot-Lau interferometer to the best spectrum for a knee phantom. It turns out that cartilage can be visualized with an effective dose of 1.16 mSv.